A ground-based Global Positioning System (GPS) network which consists of 147 uniformly distributed stations has been implemented in Turkey in May 2009. Precipitable water (PW) data estimated using this network is available since October 2010. Three experiments for a specific heavy snow case have been conducted to assess the impact of assimilation of this new data on short range weather forecasts. Verifications with surface observations indicate some reduction in the biases of basic variables for whole domain, and improvement in precipitation forecasts. Upper air variables of all simulations are compared with radiosonde observations, and some improvement in dew point temperatures through troposphere is observed with cycling mode assimilation.